1. Field of the Invention
The present invention relates to a wire saw drive apparatus for circularly driving an endless cutting wire under a predetermined tension to cut off a ferroconcrete structure, for instance.
2. Description of the Prior Art
Conventionally, wire saw drive apparatus are used for quarrying stone in stone pits. The drive apparatus includes a carriage; a wire drive pulley rotatably supported by the carriage; pulley drive means for rotating the wire drive pulley on the carriage to circularly drive an endless cutting wire reeved around the wire drive pulley and an object to be cut; a pair of adjust pulleys rotatably supported by the carriage near the wire drive pulley, for guiding a tensile side and a loose side of the cutting wire and for adjusting an reeving angle of the cutting wire relative to the wire drive pulley; and carriage drive means for moving the carriage and maintaining the cutting wire under a desired tension during cutting operation.
Although the wire saws have mainly been used for cutting stone in stone pits, the present inventor has had an idea such that the wire saw could be applied to partial cutting of ferroconcrete structure in a building, a bridge, a subway etc. and also found that the wire saw cutting method can not only be applied to the ferroconcrete cutting work but also has various advantages such that there exists no limitation of an cutting area of an object to be cut; the cutting speed is high; the cutting work is safe, etc. as compared with the conventional disk blade cutting method.
However, when the prior-art wire saw drive apparatus is used as it is for cutting an object such as ferroconcrete structure, there exists a serious problem in that the cutting wire is easily broken by tension instantaneously increased when the cutting position changes from concrete material to reinforcing iron material during the cutting operation or when the moving cutting wire is caught by or eats into a sharpened cutoff steel end.